Buspar (Buspirone) Side Effects
Buspirone commonly causes dizziness (12%), nausea (8%), headache (6%), drowsiness (10%), and nervousness (5%), with these side effects being generally mild to moderate in severity. 1
Most Common Side Effects (≥5% incidence)
Based on FDA-approved labeling from controlled clinical trials, the following side effects occur more frequently with buspirone than placebo 1:
Central Nervous System
- Dizziness: 12% (vs 3% placebo) - most common CNS effect
- Drowsiness: 10% (vs 9% placebo)
- Nervousness: 5% (vs 1% placebo)
Gastrointestinal
- Nausea: 8% (vs 5% placebo) - most common GI effect
- Dry mouth: 3%
- Abdominal/gastric distress: 2%
General
- Headache: 6% (vs 3% placebo)
- Fatigue: 4%
- Lightheadedness: 3%
- Excitement: 2%
Side Effects Leading to Discontinuation
Approximately 10% of patients discontinued buspirone in premarketing trials due to adverse events 1. The most common reasons included:
- CNS disturbances (3.4%): primarily dizziness, insomnia, nervousness, drowsiness, lightheadedness
- GI disturbances (1.2%): primarily nausea
- Miscellaneous (1.1%): primarily headache and fatigue
Comparative Side Effect Profile
Buspirone demonstrates a notably different side effect profile compared to benzodiazepines 2:
- Drowsiness occurs significantly LESS with buspirone (9%) versus diazepam (32%), clorazepate (26%), lorazepam (58%), or alprazolam (43%)
- No sedation or psychomotor impairment - a key advantage over benzodiazepines
- Dizziness and nausea occur MORE frequently with buspirone than benzodiazepines 2, 3
Less Common but Notable Side Effects
Frequent (1-10% incidence) 1:
- Insomnia: 3%
- Confusion: 2%
- Anger/hostility: 2%
- Depression: 2%
- Blurred vision: 2%
- Diarrhea: 2%
- Constipation: 1%
- Tachycardia/palpitations: 1%
- Tremor: 1%
- Weakness: 2%
Infrequent (0.1-1% incidence) 1:
- Cardiovascular: syncope, hypotension, hypertension
- CNS: depersonalization, dysphoria, euphoria, akathisia, hallucinations, involuntary movements, suicidal ideation, seizures
- GI: flatulence, anorexia, increased appetite
- Genitourinary: urinary frequency, menstrual irregularity
- Musculoskeletal: muscle cramps, muscle spasms
- Sexual: decreased or increased libido
Rare (<0.1% incidence) 1:
- Serious cardiovascular: cerebrovascular accident, congestive heart failure, myocardial infarction
- CNS: psychosis, stupor, slurred speech
- Sexual: delayed ejaculation, impotence
- Hematologic: eosinophilia, leukopenia, thrombocytopenia
Important Clinical Considerations
Dose-Related Effects
Nausea, dizziness, and somnolence are dose-related 4, 3. A meta-analysis found that buspirone 15 mg twice daily had a similar adverse event profile to 10 mg three times daily, except for significantly more palpitations with BID dosing (5% vs 1%) 4.
Cognitive Effects
Buspirone may actually improve cognitive function rather than impair it 5. A 2024 meta-analysis demonstrated significant cognitive benefits, particularly in:
- Visual learning and memory
- Logical reasoning
- Attention
This contrasts sharply with benzodiazepines, which impair cognition.
Serious Neuropsychiatric Concerns
Rare cases of worsening psychosis have been reported 6. Buspirone acts as a dopamine D2/D3/D4 antagonist, which paradoxically can increase dopaminergic metabolites rather than produce antipsychotic effects. Monitor patients with psychotic disorders closely.
Serotonin Syndrome Risk
Buspirone can contribute to serotonin syndrome when combined with other serotonergic agents 7. A case report documented serotonin syndrome (confusion, diaphoresis, incoordination, diarrhea, myoclonus) when buspirone was added to fluoxetine. Exercise caution when combining with SSRIs, SNRIs, or other serotonergic drugs.
Route of Administration
Intranasal administration significantly increases bioavailability and adverse effects 6. Oral buspirone has only ~4% bioavailability due to first-pass metabolism. Intranasal use bypasses this and can lead to enhanced dopaminergic effects and worsening psychosis.
Key Clinical Pearls
- Onset timing: Most adverse effects emerge within the first few weeks of treatment 8
- Severity: Side effects are predominantly mild to moderate 2
- No withdrawal syndrome: Unlike benzodiazepines, buspirone does not cause physical dependence
- No psychomotor impairment: Safe for activities requiring alertness
- Delayed efficacy: May take 2-4 weeks to become effective 8, so early side effects may occur before therapeutic benefits